As soon as your baby becomes trained to go the bathroom independently then you can begin them to the washroom alone, but you need to make sure they have no troubles. To avoid any problem you need to make sure you buy them a toilet seat of their size. You can look for kids toilet seat from https://raab.com.sg/collections/potty and find a comfortable seat for them.
When training your kid to go to the bathroom it's necessary not to scold them should they refuse to sit on the potty or should they can't just go. This is only because they may start to associate visiting the bathroom with poor behavior, you wish to promote this behavior and show positive signals.
Don't get frustrated when the first couple of visits they sit on the potty seat they don't urinate, as it may be new of them.
As for the colors, there are a few you can find that mostly depend on the manufacturer. Some manufacturers offer one or two color options, while others offer multiple colors for specific models.
Most of these seats are made of injection-molded polypropylene which is anti-dirt material. This can give the seat a permanent look, meaning you won't have to change the toilet seat frequently. And these seat ends are great and give the bathroom an overall elegant look.